Answer:
A) 6,3
Why?
The midpoint, which is somewhat self-explanatory thanks to its name, is a point in the center of a line.
To answer this question properly, you need to analyze the line and assess the situation.
How did it go from x = 2 to x = 10? Let's see, if we count by two's across the line, you'll notice it makes more sense. So now we know that every square goes up by two. x = 6 is the exact center of the line.
I hope this wasn't confusing, it's tough to explain it!
